Automated fiber placement machines are widely used to manufacture parts, components and structures from composite material. The materials used in automated fiber placement are typically composed of longitudinal fibers and resin consolidated into tapes, or thin strips, commonly known as “tows.” Anywhere from a single tow to several of the tows arranged side-by-side are fed out of the fiber placement machine as the fiber placement machine lays and compacts a “ply” or “course” over and onto a tool. The number of tows released by the fiber placement machine and placed over and onto the tool depends on several factors, including, for example, the size, dimensions, shape, and contour of the tool. As each ply or course is laid upon a previously laid and compacted ply or course, a composite part is built up and formed, in layer-by-layer fashion, upon the tool.
The automated fiber placement process generally described above enables the construction of complex composite structures having steered or curvilinear fiber paths. This method of producing composite structures is more cost effective than manual methods. It also provides an improved structural efficiency due to its ability to orient the fibers along local internal loads paths, which potentially results in lighter and stronger structures and a lower cost of making the part when compared to structures made by other production methods.
During the automated fiber placement process, the tows are typically heated as they are being laid over and onto the tool or over a previous layer of tows. The heat supplied to the tows causes them to become tacky (a.k.a., sticky). When tacky, the individual tows bond and join together with adjacent or proximate tows to form a cohesive ply or composite part.
Unfortunately, the fiber placement machinery today is limited in its use partially due to the inability to quickly heat the tool or the carbon fiber tows proximate the point of application and compaction. Previous methods of heating require complex, expensive assemblies and use the heat transfer method of convection. Blowing hot air in the direction of the tool or the previously laid tows is a somewhat effective heating method, but it is slow reacting and is much more difficult to control.
The invention provides a system and method of heating the tool or the previously laid tows proximate the point of application and compaction without the associated problems and drawbacks existing with the current methods and apparatuses. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.